Wavelength-selective 1XN² switches with two-dimensional input/output fiber arrays
A 1×N2 wavelength selective switch (WSS) configuration in which switch elements are configured in a way that enables the input or output fibers to be arranged in a two-dimensional (2D) array. By employing 2D arrays of input/output channels, the channel count is increased from N to N2 for wavelength selective switches. In one embodiment, in which the components are arranged as a 2-f imaging system, a one-dimensional (1D) array of mirrors is configured such that each mirror has a dual scanning axis (i.e., each mirror can be scanned in X and Y directions). In another embodiment, in which the components are arranged as a 4-f imaging system, two 1D arrays of mirrors are configured with orthogonal scanning directions. In both embodiments, the number of ports is increased from N to N2.
This application is a continuation of U.S. application Ser. No. 11/053,182 filed on Feb. 7, 2005, now U.S. Pat. No. ______, incorporated herein by reference in its entirety, which is a 35 U.S.C. § 111(a) continuation of PCT international application serial number PCT/US03/17043 filed on May 30, 2003 which designates the U.S., incorporated herein by reference in its entirety, and which claims priority from U.S. provisional application Ser. No. 60/402,387 filed on Aug. 8, 2002, incorporated herein by reference in its entirety. Priority is claimed to each of the foregoing application.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENTThis invention was made with Government support under Grant No. N66001-00-C-8088, awarded by DARPA/SPARWAR. The Government has certain rights in this invention.
INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISCNot Applicable
NOTICE OF MATERIAL SUBJECT TO COPYRIGHT PROTECTIONA portion of the material in this patent document is subject to copyright protection under the copyright laws of the United States and of other countries. The owner of the copyright rights has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the United States Patent and Trademark Office publicly available file or records, but otherwise reserves all copyright rights whatsoever. The copyright owner does not hereby waive any of its rights to have this patent document maintained in secrecy, including without limitation its rights pursuant to 37 C.F.R. § 1.14.
BACKGROUND OF THE INVENTION1. Field of the Invention
The present invention pertains generally to wavelength-selective switches (WSS), and more particularly to a 1×N2 WSS that uses a two-dimensional array of input/output fibers whereby the number of output ports are significantly increased.
2. Description of Related Art
Wavelength-selective switches (WSS) that support individual wavelength switching are of great interest for transparent optical networks. Recent advances in WSS technologies have revolutionized optical fiber communication networks. Wavelength-selective switches have received a great deal of attention because their ability to route different wavelength channels independently. For example, Ford et al. proposed the first MEMS (Micro-Electro-Mechanical Systems)-based optical add/drop multiplexer (OADM) using a digital micromirror array (J. E. Ford, V. A. Aksyuk, D. J. Bishop, and J. A. Walker, “Wavelength add-drop switching using tilting micromirrors,” J. Lightwave Technology, vol. 17, p. 904-11, 1999, incorporated herein by reference). The use of MEMS micromirrors offers lower insertion loss and faster speed than liquid-crystal-based OADM (J. S. Patel and Y. Silberberg, “Liquid crystal and grating-based multiple-wavelength cross-connect switch,” IEEE Photon. Technol. Lett., 7, 514-516 (1995), incorporated herein by reference). This OADM is essentially a 1×1 wavelength-selective switch; however, a multiport wavelength-selective switch can be realized by replacing the digital micromirrors with analog micromirrors and expanding the input/output fibers into a linear array. This is a useful network element because it can be used either as a versatile multiport add-drop multiplexer or as a basic building block for N×N wavelength-selective crossconnect (WSXC).
Several 1×N WSS configurations also have been reported. Examples of such configurations as described in D. M. Marom, et al., “Wavelength-selective 1×4 switch for 128 WDM channels at 50 GHz spacing,” 2002 Optical Fiber Communication (OFC) Conference, Postdeadline Papers (FB7), Anaheim, Calif., Mar. 17-24, 2002, FB7, incorporated herein by reference; A. R. Ranalli, B. A. Scott, J. P. Kondis, “Liquid crystal-based wavelength selectable cross-connect,” ECOC 1999, incorporated herein by reference; T. Ducellier, et al., “The MWS 1×4: a high performance wavelength switching building block,” ECOC 2002, incorporated herein by reference; and S. Huang, J. C. Tsai, D. Hah, H, Toshiyoshi, and M. C. Wu, “Open-loop operation of MEMS WDM routers with analog micromirror array,” 2002 IEEE/LEOS Optical MEMS Conf., incorporated herein by reference.
Such switches are basic building blocks for N×N fully non-blocking wavelength-selective optical crossconnect. In current switch designs, however, the port count is limited by optical diffraction. Note that the switches reported to date are generally limited to 1×4, though adding circulators to each port can double the port count.
For example,
It will be appreciated that larger port count (≧10) WSS configurations are needed for high capacity networks. The present invention satisfies that need, as well as others, and overcomes limitations in current WSS switch designs.
BRIEF SUMMARY OF THE INVENTIONThe present invention comprises a 1×N2 wavelength selective switch (WSS) configuration. In accordance with an aspect of the invention, the input or output fibers are arranged in a two-dimensional (2D) array rather than in a one-dimensional (1D) array.
The present invention provides for a larger number of input or output channels compared to previously developed configurations. By employing 2D arrays of input/output channels, the channel count is increased from N to N2 for wavelength selective switches.
By way of example, and not of limitation, a switch configuration according to the present invention comprises a wavelength dispersive element, at least one focusing lens, and at least one mirror array. In one embodiment, a one-dimensional (1D) array of mirrors is configured such that each mirror has a dual scanning axis (i.e., each mirror can be scanned in X and Y directions). In another embodiment, two 1D arrays of single-axis mirrors are configured with orthogonal scanning directions. In both embodiments, the number of ports is increased from N to N2. In the embodiment using an array of dual-axis mirrors, the switch is configured as a 2-f system. In the embodiment using two arrays of single-axis mirrors, the switch is configured as a 4-f imaging system.
Further aspects of the invention will be brought out in the following portions of the specification, wherein the detailed description is for the purpose of fully disclosing preferred embodiments of the invention without placing limitations thereon.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)The invention will be more fully understood by reference to the following drawings which are for illustrative purposes only:
Referring more specifically to the drawings, for illustrative purposes the present invention is embodied in the apparatus generally shown in
Referring first to
Those skilled in the art will appreciate that the wavelength dispersive element 16 can be a conventional type grating, such as a diffraction grating. In addition, imaging components such as lenses 20 used as means to focus the optical beams onto the mirrors can be microscopic or macroscopic optical elements, lenslets in combination with bulk lenses, and the like.
It will further be appreciated that the mirror arrays would preferably comprise Micro-Electro-Mechanical Systems (MEMS) micromirror arrays for both size and reliability considerations. However, control of dual-axis micromirrors is more complex than control of single-axis mirrors. Accordingly, in a second embodiment, instead of using an array of dual-axis mirrors, two 1D arrays of single-axis mirrors are configured with orthogonal scanning directions. As can be seen in the optical switch 100 shown in
In the optical switch 100 shown in
It will be appreciated that the embodiments described above illustrate a 2D output fiber array 56. However, the optical switch can be implemented in either a 1×N2 configuration where the 2D fiber array is the output array or in a N2×1 configuration where the 2D fiber array is the input array. Therefore, it will also be appreciated that an optical switch according to the present invention comprises at least one input channel and at least one output channel, wherein either the input channel or the output channel comprises a 2D fiber array. It will further be appreciated that an optical beam can be switched from any input fiber to any output fiber.
EXAMPLE 1 A prototype system according to the embodiment shown in
A prototype system according to the embodiment shown in
As discussed above, discrete collimators can be used in the embodiments of the invention heretofore described. The examples set forth above relied on the use of discrete collimators to simulate a 2D collimator array. However, the large housings of discrete collimators tend to reduce the practical port count, and the alignment of individual collimators is a cumbersome process. On the other hand, it will be appreciated that a monolithic 2D fiber collimator array can overcome the above disadvantages. Accordingly, referring to
A prototype system was constructed according to the embodiment shown in
As can be seen, therefore, an advantage of the present invention over existing practices is that use of a 2D fiber array increases the number of fiber ports from N to N2, where N is the number of input/output ports for a 1D fiber array configuration. Accordingly, the invention facilitates the implementation of multi-port optical add-drop multiplexers with >10 output ports which are desired for dense wavelength division multiplexed (DWDM) networks. By optimizing the mirror and collimator sizes, the port count of the system can be expanded considerably.
Furthermore, it will be appreciated that the invention can achieve these advantages using conventional lenses, gratings, and the like. Additionally, various micromirror and actuator designs can be used for the micromirrors, including, but not limited to, those described in U.S. Pat. No. 6,097,859, incorporated herein by reference, those described in Hah, S. Huang, H. Nguyen, H. Chang, H. Toshiyoshi, and M. C. Wu, “A low voltage, large scan angle MEMS micromirror array with hidden vertical comb-drive actuators for WDM routers,” 2002 Optical Fiber Communication (OFC) Conference, Anaheim, Calif., Mar. 17-24, 2002, incorporated herein by reference, and those described in D. Hah, S. Huang, H. Nguyen, H. Chang, J. C. Tsai, and M. C. Wu, “Low voltage MEMS analog micromirror arrays with hidden vertical comb-drive actuators,” Solid-State Sensor, Actuator, and Microsystems Workshop, June 2002, p. 11-14, incorporated herein by reference.
Although the description above contains many details, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments of this invention. Therefore, it will be appreciated that the scope of the present invention fully encompasses other embodiments which may become obvious to those skilled in the art, and that the scope of the present invention is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.” All structural, chemical, and functional equivalents to the elements of the above-described preferred embodiment that are known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the present claims. Moreover, it is not necessary for a device or method to address each and every problem sought to be solved by the present invention, for it to be encompassed by the present claims. Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. No claim element herein is to be construed under the provisions of 35 U.S.C. 112, sixth paragraph, unless the element is expressly recited using the phrase “means for.”
Claims
1-41. (canceled)
42. A method of optically switching multiple wavelengths to and from a two-dimensional array of optical ports, comprising:
- controlling the single-axis angular position of rotating micromirror elements within a first and second micromirror array;
- receiving an optical beam containing multiple wavelengths from a two-dimensional array of optical ports;
- dispersing wavelength components of said optical beam which reflect from a wavelength dispersive element;
- reflecting said wavelength components from micromirror elements of the first micromirror array in a first plane toward the second micromirror array in a second plane;
- reflecting said wavelength components from micromirror elements in said second micromirror array in the second plane toward said first micromirror array;
- reflecting said wavelength components from micromirror elements in said first micromirror array toward said wavelength dispersive element; and
- directing an optical beam containing said wavelength components from said wavelength dispersive element to said two-dimensional array of optical ports.
43. A method as recited in claim 42, wherein said wavelength dispersive element comprises a diffraction grating.
44. A method as recited in claim 42, wherein said diffraction grating is disposed proximal the path between said first and second micromirror arrays.
45. A method as recited in claim 42, wherein micromirrors within said micromirror array comprises micro-electro-mechanical systems (MEMS) micromirrors.
46. A method as recited in claim 42, further comprising at least one imaging component configured for positioning said optical beam onto said first array, said second array, or a combination of said first and second array of actuated mirrors.
47. A method as recited in claim 46, wherein said imaging component comprises at least one lens.
48. A method as recited in claim 42, wherein said first plane and said second plane are configured in a 4-f confocal arrangement.
49. A method as recited in claim 42, wherein said diffraction grating lies equal distance between said first micromirror array and said second micromirror array.
50. A method as recited in claim 49:
- wherein at least one imaging component comprises at least one lens; and
- wherein said at least one lens is disposed between said diffraction grating and said first micromirror array and said second micromirror array.
51. A method as recited in claim 42, wherein micromirrors in said second micromirror array are configured for rotating in a single axis which is orthogonal to the axis of rotation for said first micromirror array.
52. A method of optically switching multiple wavelengths to and from a two-dimensional array of optical ports, comprising:
- controlling the single-axis angular position of rotating micromirror elements within a first and second micromirror array;
- receiving an optical beam containing multiple wavelengths from a two-dimensional array of optical ports;
- dispersing wavelength components of said optical beam which reflect from a wavelength dispersive element;
- focusing said wavelength components received from said wavelength dispersive element through a first imaging component to a first plane;
- rotating micromirror elements within a first micromirror array located on said first plane, each micromirror in said first micromirror array configured for rotation about a single axis;
- reflecting said wavelength components from said micromirror elements to said first imaging component assembly;
- directing said wavelength components from said first imaging component assembly to a second imaging component;
- focusing said wavelength components through said second imaging component to a second plane;
- rotating micromirror elements within a second micromirror array located on said second plane, each micromirror in said second micromirror array configured for rotation about a single axis in response to said micromirror deflection signal;
- reflecting said wavelength components from said micromirror elements to said second imaging component;
- directing said wavelength components through said second imaging component to said first imaging component;
- focusing said wavelength components through said first imaging component to said first micromirror array in said first plane;
- reflecting said wavelength components from said first micromirror array back to said first imaging component;
- directing said wavelength components through said first imaging component to said wavelength dispersive element; and
- directing an optical beam containing said wavelength components from said wavelength dispersive element to said two-dimensional array of optical ports.
53. A method as recited in claim 52, wherein said wavelength dispersive element comprises a diffraction grating.
54. A method as recited in claim 52, wherein said first and/or second imaging components comprise at least one lens.
55. A method as recited in claim 52, wherein the single axis rotation of micromirrors in said second micromirror array is orthogonal to the rotation of micromirrors in said first micromirror array.
56. A method as recited in claim 52, wherein said first plane and said second plane are positioned in a 4-f confocal arrangement.
57. A method as recited in claim 52, wherein said wavelength dispersive element lies equal distance between said first micromirror array and said second micromirror array.
58. A wavelength selective optical switch, comprising:
- a two-dimensional array of optical ports configured for communicating optical beams containing multiple wavelength components, and having a plurality of ports including a first and second port;
- a wavelength dispersive element configured for separating at least one wavelength component in said optical beams from at least one other wavelength component in said optical beams;
- a first array of single-axis actuated mirrors; and
- a second array of single-axis actuated mirrors;
- wherein said first and second arrays of actuated mirrors are configured for switching the wavelength components of said optical beam from said first port to a second port within said two-dimensional array of optical ports.
59. A wavelength selective optical switch as recited in claim 58, wherein said second array of mirrors is configured with a scanning direction that is orthogonal to said first array of mirrors.
60 A wavelength selective optical switch as recited in claim 58, wherein said first and second array of mirrors are configured in a 4-f confocal arrangement centered on said wavelength dispersive element.
61. A wavelength selective optical switch as recited in claim 58, further comprising at least one imaging component configured for positioning said optical beam onto said first array, or said second array, or a combination of said first and second arrays of actuated mirrors.
62. A wavelength selective optical switch as recited in claim 58, further comprising means for collimating optical beams in said optical switch.
63. A wavelength selective optical switch as recited in claim 62, wherein said means for collimating optical beams in said optical switch comprises a monolithic two-dimensional collimator array.
64. A wavelength selective optical switch as recited in claim 58, wherein said wavelength selective optical switch is a component of an N×N fully non-blocking wavelength-selective optical crossconnect.
65. A wavelength selective optical switch as recited in claim 58, wherein said wavelength selective optical switch is a component of an optical network.
Type: Application
Filed: May 30, 2006
Publication Date: Dec 28, 2006
Patent Grant number: 7336867
Inventors: Ming-Chiang Wu (Orinda, CA), Jui-Che Tsai (Berkeley, CA)
Application Number: 11/444,146
International Classification: G02B 6/26 (20060101);